Torsional damping device, especially for clutches

ABSTRACT

A torsion damping device is mounted between two coaxial rotating members for transmitting a rotary toque from one member to the other with damping of vibrations and torque oscillations the damping device comprising, two rings coaxial with the rotating members, rotational coupling means between the two rotating members and the rings, circumferentially acting resilient members mounted between the rings in housing which are formed in the rings and which include a device for abutment of the ends of the resilient members, the two rings are rotatable with respect to each other and with respect to the two rotating members with a limited angular displacement, and are urged in opposite directions of rotation by the resilient members and toward abutment on the device for coupling them to the respective ones of the rotating members.

SUMMARY OF THE INVENTION

This invention relates to a torsion damping device which is mountedbetween two coaxial rotating members for transmitting a rotationaltorque between the two said members, with damping out of vibrations andtorque oscillations, and it is applicable in particular to frictionclutches for motor vehicles.

Conventionally, a torsion damper includes two guide rings which arecoaxial with the two rotating members and which are coupled for rotationwith each other and with one of the rotating members, an annular damperplate disposed between the two guide rings, and means for coupling thesaid annular damper plate in rotation to the other rotating member.Circumferentially acting resilient members, such as helical springs, aremounted between corresponding windows of the damper plate and the guiderings, and are in engagement at their ends on the radial edges of thesaid windows so as to transmit a rotational torque between the guiderings and the annular damper plate, while absorbing vibrations andtorque oscillations by elastic deformation.

The axes of the said springs a-re in the plane of the annular damperplate, in such a way that, during angular displacement between the guiderings and annular damper plate, one end of each spring is in axialabutment on a radial edge of a window in the annular damper plate, whileits other end is in abutment on the radial edges of the windows in theguide rings, substantially symmetrically with respect to the plane ofthe annular damper plate, with the resultant of the forces applied atthe said other end of a spring being axial with respect to the spring.In such a torsion damper, the springs work in axial compression, whichis beneficial to the length of their useful life.

In order to reduce the number of components and the axial size, and alsothe cost, of such a torsion damper, it has previously been proposed toreplace the known structure having two guide rings and an annular damperplate with a simpler structure which only has two rings, one of which iscoupled in rotation to one rotating member, the above mentioned springsbeing disposed between these two rings in housings which are defined bywindows or cavities in the said rings. During an angular displacementbetween the two rings, each spring is in abutment at one end on a radialedge of a window of one ring, and at its other end on a radial edge of awindow of the other ring, but these abutments are offset with respect tothe axis of the spring, so that the compression forces from the springsare no longer axial but are oriented diagonally, and the compression ofthe springs is accompanied by bending which tends to displace them withrespect to the axis. In order to avoid such displacement, it isnecessary to provide means for guiding the springs, which give rise tofriction effects liable to disturb the operation of the torsion damper.It is also necessary to over-dimension the springs so that they supportthe additional stresses caused by their being compressed diagonally.

A main object of the present invention is to overcome these drawbacks inthe known art, but without in so doing increasing the number ofcomponents, nor the axial size or cost of a torsion damper of the typedescribed above.

To this end, it proposes a torsion damping device, mounted between twocoaxial rotating members for transmitting a rotary torque from onemember to the other with damping of vibrations and torque oscillations,comprising:

two rings coaxial with the two rotating members,

rotational coupling means between the two rotating members and therings,

circumferentially acting resilient members mounted between the rings inhousings which are formed in the said rings and which include means forabutment of the ends of the resilient members,

characterised in that the two rings are rotatable with respect to eachother and with respect to the two rotating members with a limitedangular displacement, and are urged in rotation by the said resilientmembers in opposite directions tending to put them into abutment on themeans for coupling them to the respective ones of the rotating members.

In the device according to the invention, and by contrast with what isfound in the known art, each ring is rotatable with respect to the tworotating members and with respect to the other ring, independently ofthat other ring. This then enables a first ring to be associated with afirst rotating member and the second ring with the second rotatingmember in one direction of rotation, and conversely, the first ring withthe second rotating member and the second ring with the first rotatingmember in the other direction of rotation, so that it enables the twodirections of rotation to be distinguished from each other.

Each ring acts in only one direction on the resilient members, and eachresilient member is in constant engagement at one end on an element ofone ring, and at its other end on an element of the other ring. Thisresults in improved engagement and improved holding of the resilientmembers, together with a reduction in wear of the latter and an increasein their useful life.

In addition, because of the constant engagement of the resilient membersat each of their ends, it is of advantage to make use of elastomericblocks as resilient members, in place of the traditional helicalsprings.

Fitting of the device according to the invention is also more simplethan in the known art, because none of the rings has to be coupled inrotation with a rotating member, and this avoids operations of seamingor the like which are used in the known art. Consequently, renovationand maintenance of the clutch are also simplified.

The two rings are preferably identical. According to another feature ofthe invention, each ring is in engagement on the means for coupling thesaid ring to one of the rotating members, and a circumferentialclearance exists between the said ring and the means for coupling it tothe other rotating member.

This, in particular, reduces shocks and damage to the rings and/or theircoupling means, in operation.

In a first embodiment of the invention, the two rings are made bypress-forming or moulding with the housings of the above mentionedresilient members, each housing having at one of its ends an axialengagement face for an elastic member placed in the said housing.

The opposite end of the housing does not have any axial engagement meansfor the resilient member.

Preferably, the housings are defined in the said rings by recesses whichare situated face to face as between one ring and the other, each recessbeing joined at one end to a boss which projects towards the other ringso as to define the axial engagement face of a said resilient member.

In a further embodiment of the invention, the said rings are flat andthe housings of the resilient members are defined by windows in therings, with each window having a radial side which serves as an axialabutment for a resilient member and which includes means for centringand retaining that member.

These two rings are simple and inexpensive to make, and can be mountedin engagement on each other.

According to a further feature of the invention, each ring includes aset of teeth meshing, with a predetermined circumferential clearance,with a set of teeth of one of the said rotating members.

The set of teeth of the rings are formed on their inner periphery, andthe set of teeth of the said rotating member is formed, for example, onthe outer periphery of a cylindrical surface of the said rotatingmember.

When the rings urged into rotation by the said resilient members inopposite directions are in abutment on the said rotating member, theteeth of one ring are in engagement on the flanks of the teeth of therotating member and the teeth of the other ring are in engagement on theopposed flanks of the teeth of the said rotating member.

The means for coupling the rings in rotation to the other one of therotating members comprise, for example, fingers fixed to the saidrotating member and engaged in circumferential slots of the said rings,the slots being of limited angular extent.

Preferably, at least one slot of one ring is positioned with respect toa slot of the other ring in such a way that the same finger fixed to thesaid rotating member passes through the two said slots.

In another version, the means connecting the said rings to one of therotating members comprise lugs fixed to the rings and engaged betweenabutments carried by the rotating member, the said lugs beingsubstantially radial.

According to yet another feature of the invention, the torsion dampingdevice constitutes a unitary assembly, the two rings being in hookedengagement on each other by means of circumferential lugs offset axiallyso as to engage within each other and to oppose axial separation of therings.

The said unitary assembly can thus be pre-assembled and then fitted onthe rotating members.

The device according to the invention can be used for absorption anddamping of vibrations and torque oscillations between two rotatingmembers of any type whatsoever.

It can also be used as a main damper and/or as a predamper in a torsiondamper of a friction clutch for a motor vehicle.

Where it constitutes a predamper mounted in series with a main damper ina clutch, it can be mounted either inside the main damper or on theoutside of the latter, with a very much reduced axial size.

The invention will be better understood, and further features, detailsand advantages of it will appear more clearly on a reading of thefollowing description, which is given by way of example and withreference to the attached drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a first embodiment of a device according tothe invention;

FIG. 2 is an exploded perspective view of the same device shown partlycut away;

FIG. 3 is a diagrammatic partial front view of a modified version of thedevice according to the invention;

FIG. 4 is an exploded perspective view, partly cut away, of a furthermodified version of the device;

FIG. 5 is a front view of the device in FIG. 4;

FIG. 6 is a side view of the device shown in FIG. 5;

FIG. 7 is a partial view, in axial cross section, of a torsion damperfor a clutch, including a device according to the invention;

FIG. 8 is a diagrammatic partial view in axial cross section of thedamper of FIG. 7, equipped with the version which is shown in FIG. 3;

FIGS. 9 and 10 are diagrammatic views in axial cross section of twofurther modified versions;

FIG. 11 is a diagrammatic partial view in axial cross section of theversion in FIG. 3, mounted in a torsion damper of another type;

FIG. 12 is a diagrammatic partial view in axial cross section of thedamper in FIG. 11, equipped with the device shown in FIGS. 1 and 2;

FIG. 13 is a half view in axial cross section of a modified version.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is first made to FIGS. 1 and 2, to describe a first embodimentof the device according to the invention. In these Figures, thereference 10 designates a rotating member which is here in the form of acylindrical hub having an external peripheral set of teeth, the teeth 12of which extend parallel to the axis over part of the length of the hub10.

A further rotating member, not shown in FIGS. 1 and 2 and coaxial withthe member 10, carries cylindrical fingers 14 which extend parallel tothe axis of the member 10, radially on the outside of the said member.

The device according to the invention, the purpose of which is to dampout oscillations and irregularities in the rotary torque between thesetwo rotating members, comprises two identical rings 16, 18 which aremounted face to face on the rotating member 10, and each of which has aset of teeth at its inner periphery, the teeth 20 of which are in meshwith the teeth 12 of the first member 10 with a predeterminedcircumferential clearance.

In the drawings, the rings 16, 18 have been shown partly cut away toassist understanding, but it has to be understood that each of them iscontinuous over 360° about the axis of rotation.

The rings 16, 18 have circumferential slots 22 extending over a smallangle, the slots 22 of one ring being arranged to be positioned withrespect to the slots 22 of the other ring in such a way that the samecylindrical fingers 14 fixed to the other rotating member pass throughthem.

The rings 16, 18 also include circumferentially oriented, substantiallysemicylindrical, housings 24 arranged to receive elastically deformablemembers such as helical springs 26, the length of which correspondssubstantially to that of the housings 24. Each housing 24 is open at oneend in a boss 28 which projects on the ring towards the opposed ring,and which has a substantially semicircular or U-shaped contour, theopening of which is oriented radially outwards. The semicylindricalhousing 24 terminates substantially in the middle of the boss 28, andhas an end face 30 which is substantially flat and extends at rightangles to the plane of the ring, and which joins the peripheral wall ofthe housing 24 to the base wall of the boss 28, to define an axialabutment face for one end of the elastic member 26 fitted in thathousing 24. The other end 32 of the housing 24 has, at right angles tothe plane of the ring, a dimension which is smaller than one half of thetransverse dimension of the elastic member 26. Thus, when the rings 16and 18 are face to face, and when their housings 24 are substantiallyfacing each other, a resilient member, 26 placed between the rings intwo mutually facing housings 24 will engage axially at one end on theend face 30 of a housing 24 of one ring, and at its other end on the endface 30 of the housing 24 in the other ring.

The slots 22 in the rings 16, 18 are arranged, with respect to thehousing 24 and the cylindrical fingers 14 which are fixed in rotation tothe other driving member, in such a way that, when the two rings aremounted on the member 10 in face to face relationship as shown in FIG.1, with the,resilient members 26 being within the housings 24, the saidmembers 26 urge the two rings into rotation in opposite directions andtend to bring the ends of the slots 22 into abutment on the cylindricalfingers 14, in the direction indicated by the arrow 34 in FIG. 1 for thering 18, and in the direction indicated by the arrow 36 for the ring 16.In this position, the teeth 20 of the ring 18 are urged against theflanks 12 a of the teeth 12 of the first rotating member 10, and theteeth 20 of the other ring 16 are urged on the opposed flanks 12 b ofthese teeth 20. In other words, the ring 16 cannot turn with respect tothe two rotating members except in the direction of the arrow 34, andthe ring 18 can only turn with respect to these two members in thedirection of the arrow 36.

Preferably, in the position of FIG. 1, each ring is in abutment on themeans by which it is coupled with one of the rotating members, and aclearance exists between this ring and the means coupling it with theother rotating member.

In operation, when a vibration or torque irregularity results inrelative rotation of the first rotating member with respect to the otherone in the direction of the arrow 34, the ring 18 is held fast againstrotation with respect to the other rotating member due to the fact thatthe cylindrical fingers 14 fixed to that other rotating member are inengagement on the base of the slots 22 of the ring 18, thus preventingits rotation in the direction of the arrow 34, while the other ring 16is displaced in rotation in the direction of the arrows 34 with respectto the other rotating member by means of the teeth 12 of the firstmember 10, which are in engagement, in this direction of rotation, onthe teeth 20 of the ring 16. The ring 16 is then turning with respect tothe other rotating member until the base of the slots 22 in the ring 16come into engagement on the cylindrical fingers 14 and/or until theteeth 20 of the ring 16 come into engagement on the flanks 12 a of theteeth 12 of the first member 10. This rotation is converted into axialcompression of the resilient members 26 in the cavities 24 of the rings16, 18.

Conversely, when the first member 10 is tending to turn with respect tothe other member in the direction indicated by the arrow 36, it drivesthe ring 18 in rotation with it, the effect of which is to compress theresilient members 26 axially in the direction of the arrow 36, the ring16 being immobilised against rotation on the other rotating member.

The vibrations and irregularities in torque between the two rotatingmembers are thus absorbed by the axial compression, in either direction,of the resilient members 26 mounted in the cavities 24.

Preferably, the rings turn with respect to the rotating members, untilthe limit of the angular displacement which is also permitted betweenthe two rotating members is reached, and this avoids, if necessary, anycontacts and impacts between the bases of the slots 22 and fingers 14and/or between the teeth 20 of the ring and the flanks of the teeth 12,and also enables a rotational torque to be transmitted from one rotatingmember to the other via means which limit their relative angulardisplacement and not via the rings and the means coupling them inrotation to the rotating members.

Preferably, the rings 16 and 18 include at their outer periphery meansfor hooking them together, such as circumferential lugs 38 which areaxially offset with respect to the rings in such a way that they canengage in each other when the rings are in face to face relationship,thereby preventing the rings from becoming axially separated. The axialposition of the assembly of the rings 16, 18 on the first rotatingmember 10 is defined for example by means of an open elastic ring 40, orcirclip, which is engaged in an annular groove formed in the outerperipheral set of teeth of the first rotating member 10. The rings 16,18 are on either side of this open ring 40, and are held by the latterin an axial position on the first rotating member 10.

In the embodiment shown in FIGS. 1 and 2, the rings 16, 18 are of metaland are in the form of pressings or stampings. In another version theymay be made by moulding in any appropriate material, for example in afibre reinforced plastics material.

This device has a certain number of advantages as compared with theknown art: the rings are identical, the number of components is reduced,axial size is small, the resilient members are in permanent axialengagement at their ends and are able to be compressed under goodconditions, while assembly and fitting are simplified and assembly costis reduced.

In one modified version, the resilient members are blocks of elastomer,which behave well in compression due to the fact that their ends are inconstant abutment on the ends 30 of the housings 24.

In the modified version shown diagrammatically in FIG. 3, the deviceaccording to the invention is a predamper which is mounted in a frictionclutch for a motor vehicle, in series with a main damper which includesresiliently deformable members 42 acting circumferentially, thedimensions and stiffness of which are in particular greater than thoseof the resilient members 26 of the predamper, and which are mounted inwindows of an annular damper plate and of two guide rings (not shown),in a well known way, and which will be described with reference to FIGS.7 to 10.

In this version, the means for coupling the rings 16 and 18 of thepredamper in rotation to the said other rotating member (the annulardamper plate or one of the guide rings of the main damper) no longerconsist of cylindrical fingers 14 engaged in circumferential slots 22 inthe rings, but consist instead of radial fingers 44 of the rings 16, 18which are in abutting cooperation with the ends of the resilient members42 of the main damper.

For the rest, the structure of the device according to the invention isidentical to that described with reference to FIGS. 1 and 2.

In operation, rotation of each ring 16, 18 with respect to the rotatingmember 10 is limited by the circumferential clearance between the setsof teeth 12 and 20 of the member 10 and of the rings 16, 18, the lugs 44serving to prevent rotation of the ring 16 in the clockwise direction inFIG. 3, and rotation of the ring 18 in the opposite direction, and tolimit these rotations in the two opposed directions by angulardisplacement between the ends of the resilient members 42.

In the example shown, the lugs 44 of the rings extend radially outwardssubstantially in the plane of the rings, but could extend in differentdirections if necessary, for abutting cooperation with the ends of theresilient members 42 of the main damper.

These lugs 44, which are in overlapping pairs as shown in FIG. 3, alsomaintain the rings 16 and 18 hooked together and prevent them fromseparating axially.

In the modified version shown diagrammatically in FIGS. 4, 5 and 6, thetwo rings 46, 48 of the device according to the invention are flat, andthe housings for the resilient members 26 are circumferential windows 50of substantially rectangular form, of substantially the same length asthe resilient members 26 in the rest condition.

In order to ensure centring and retention of the resilient members 26 inthe windows 50, one radial edge of each window includes a nose 52 or thelike which is engaged in one end of the corresponding resilient member26.

For the rest, the structure of the device is similar to that describedwith reference to FIGS. 1 and 2: the two rings 46 and 48 are coupled inrotation to a first rotating member 10 by means of an internal set ofteeth 20, and to the other rotating member by means of cylindricalfingers 14 fixed to the said other rotating member and engaged incircumferential slots 54 in the rings. In addition, the rings 46 and 48are applied one on the other.

FIGS. 7 to 11 show diagrammatically various ways of incorporating adevice according to the invention in a torsion damper for a frictionclutch for a motor vehicle.

In FIGS. 7 and 8, the torsion damper comprises a main damper 60 which ismounted in series with a predamper consisting of a device according tothe invention, between an input element 62 consisting of a friction discand an output element consisting of the above mentioned rotating member10, which constitutes a cylindrical hub the inner surface of which haslongitudinal splines 64 for coupling the member 10 in rotation with anoutput shaft such as the input shaft of a gearbox. The main dampercomprises an annular damper plate 66 which carries a friction disc 62and is mounted between two identical guide rings 68 which are centredand fixed on a sleeve 70 that has a set of internal teeth meshing, witha predetermined circumferential clearance, with the external set ofteeth 12 of the member 10, and optionally an external set of teethmeshing, with a predetermined circumferential clearance, with aninternal set of teeth of the annular damper plate 66.

The above mentioned resilient members 42 of the main damper are lodgedin windows 72 and 74 formed respectively in the annular damper plate 66and the guide rings 68, while friction rings, biased axially by means ofresilient rings, are mounted between the annular damper plate 66 and atleast one of the guide rings 68, for the purpose of damping outoscillations and torque irregularities absorbed by the resilient members42 of the main damper.

The predamper consists of the device shown in FIGS. 1 and 2 and ismounted outside the main damper 60 on the set of external teeth 12 ofthe member 10. The circumferential clearance between the teeth of therings 16, 18 and the teeth 12 of the member 10 is for example greaterthan or substantially equal to the clearance between the teeth of thesleeve 70 and the member 10. The cylindrical fingers 14 which couple therings 16 and 18 in rotation to the main damper are, in this example,screws or rivets 76, extending through the slots 22 in the rings 16 and18 and mounted in appropriate apertures in one guide ring 68.

On the side of the predamper that consists of the device according tothe invention, the axial ends of the teeth 12 of the member 10 arechamfered, which enables the device according to the invention to bemounted on the member 10 by pushing it axially on to the latter, theopen elastic ring 40 expanding radially while passing over the chamferedend of the teeth 12, and closing up again radially when it reaches thelevel of the annular groove formed in the set of teeth 12 for receivingit.

The predamper consisting of the device according to the invention is inaxial abutment on the main damper, which is itself held in axialposition on the member 10 by means of a further open ring 78 on theopposite side from the predamper.

In the version shown in FIG. 8, the main damper is the same as in FIG.7, but the predamper is the one shown in FIG. 3. In this case, theradial lugs 44 of the rings 16 and 18 of the predamper are in abutmenton the ends of the resilient members 42, and couple the main damper inrotation with the rings 16, 18.

In the version in FIG. 9, the predamper is of the same type as thatshown in FIGS. 4 to 6, and the driving fingers 14 are replaced by lugs140 of the guide ring 68 of the main damper, these lugs 140 being formedon the inner periphery of the ring 68 and bent back at right anglesparallel to the axis of rotation so as to penetrate into circumferentialslots in the rings 46, 48 of the predamper.

In addition, the resilient members 26 of the predamper are lodged, nolonger in windows in the rings 46, 48, but in notches 142 in the outerperiphery of these rings, so as to reduce the radial size of thepredamper.

The latter is located axially on the hub 10 between an open ring 144mounted in an annular groove of the hub., and friction means 146 whichare biased axially on the sleeve 70 of the main damper.

In another version, the lugs 140 may be replaced by pins welded on theguide ring 68.

In a further version, the lugs 140 are replaced by a deformation of thering 68, which is obtained by a stamping operation and which is engagedaxially in slots or between radial fingers of the rings 46, 48 of thepredamper.

In the modified, version shown in FIG. 10, the predamper is similar tothat shown in FIG. 9, and it is retained axially on the hub 10, not byan open ring but by a wound elastic ring 150 which is at least partlyfitted in an annular groove of the hub 10. This ring has a plurality ofturns, the radius of which is either variable or not variable, and isformed with undulations enabling an axial force to be applied to thepredamper, in order to grip the friction rings 152 on one end of thesleeve 70 of the main damper. The predamper is coupled in rotation tothis sleeve 70 by means of fingers 14 similar to those described above.

In this embodiment, the ring 150 replaces one open ring and oneresilient ring, which reduces the number of components and makesassembly easier.

In the embodiments in FIGS. 11 and 12, the main damper is of a differenttype from those in FIGS. 7 and 8, and the predamper is mounted on themember 10 within the main damper.

In this version, the friction disc 62 is carried by a guide ring 80 ofthe main damper, and the predamper is disposed between the annulardamper plate 82 and the other guide ring 84 of the main damper.

In FIG. 11, the predamper is of the type shown in FIG. 3, and its rings16, 18 are coupled in rotation to the main damper by means of radiallugs 44 which come into abutment on the ends of the resilient members 42of the main damper.

In FIG. 12, the predamper is of the type shown in FIGS. 1 and 2, and itsguide rings 16 and 18 are coupled in rotation to the annular damperplate 82 of the main damper by means of cylindrical fingers 14 engagedin slots 22 in the rings 16, 18, and in appropriate holes formed in theannular damper plate 82 and in the guide ring 84 of the main damper.

For the rest, fitting of the predamper on the member 10 is carried outin the manner described above with reference to FIGS. 7 and 8.

Axial location of the predamper on the hub 10 can be obtained by meansof the ring 40 as shown in particular in FIGS. 7 and 8, or in any otherappropriate way, between the rings 16, 18 or on the outside of theselatter, for example by means of a “flip-flop” ring (everting ring), or abayonet fitting, and so on.

Friction means (in general a friction ring biased axially by a resilientring) are associated with the rings 16, 18 for damping out thevibrations, and are for example between the rings 16, 18 or on theoutside of these latter. In this last case, resilient rings of differentthicknesses may be used so as to give different degrees of hysteresis inboth directions of rotation.

In the embodiment in FIG. 13, a device according to the inventionconstitutes the main damper of the torsion damper mounted between thefriction disc 62 and the hub 10, and comprises two rings 88 which arepreferably identical, and which are mounted face to face on the hub 10on either side of an open ring or a median peripheral flange 90 of thehub. Each ring 88 has an internal set of teeth 92 meshing with apredetermined circumferential clearance with an external set of teeth 12of the hub 10, and also has windows 94 for mounting circumferentiallyacting resilient members 96 for absorbing vibrations and torqueirregularities, each window 94 including at one end a flange 98 foraxial abutment of one end of the resilient member 96, its other endhaving none, and axial lugs or rivets 100 are for example fixed at theouter periphery of the friction disc 62 and guided in circumferentialslots of the ring 88, or vice versa. As previously described for theforegoing embodiments, the rings 88 are biased by resilient members 96in opposite directions, so tending to bring the rivets 100 intoengagement on the ends of the above mentioned slots and the sets ofteeth 92 into engagement on the sets of teeth 12 of the hub. Theoperation of this main damper is identical to the operation alreadydescribed of the torsion damper in FIGS. 1 and 2.

The predamper in the embodiment in FIG. 13 may be of a conventional typeor may be a device according to the invention. In the latter case, thepredamper has two identical rings 102 mounted face to face on the hub 10on either side of the peripheral flange 90, and each between the flange90 and a ring 88 of the main damper.

Each ring 102 includes an internal set of teeth 104 which is inengagement, with a predetermined circumferential clearance, with a setof teeth 12 of the hub, and includes lugs 106 parallel to the axis whichare received in circumferential slots 108 of the ring 88 adjacent to theother ring 102 of the predamper, so that the lugs 106 of the two ringsinterleave with each other at the outer periphery of these rings.

Plate elements 110, projecting from the rings 102 and lugs 106,constitute axial abutments for the ends of the circumferentially actingresilient members 112 of the predamper, each resilient member 112 beingin axial engagement at one end on one plate element 110 of a ring 102and at the other end on a plate element 110 of the other ring 102.

The outer peripheries of the rings 102 are curved towards each other asshown, so as to define semicylindrical housings for the resilientmembers 112 around the peripheral flange 90 of the hub 10.

Operation of this predamper corresponds to that of the device in FIGS. 1and 2, the main damper behaving like a rigid member in response tovibrations and torque irregularities in the slow running mode, which aredesigned to be absorbed by the predamper.

At low rotational torques transmitted from the friction disc 62 to thehub 10, corresponding in particular to the slow running mode of aninternal combustion engine of a motor vehicle (the gearbox being inneutral), the disc 62 drives in rotation one of the rings 88, forexample the one on the left in FIG. 13, by engagement on the rivets 100which connect the disc to that ring. The torque is transmitted to theother ring 88 through the resilient members 96, which behave like rigidmembers because of their high stiffness. The rigid assembly formed bythe rings 88 and resilient members 96 has a slight angular clearancewith respect to the hub 10, corresponding to the angular displacement ofthe predamper. The main damper therefore transmits the torque to therings 102 of the predamper, for example from the ring 88 on the right inthe drawing to the left hand ring 102, which transmits it to the otherring 102 of the predamper through the resilient members 112 which absorbthe vibrations. Since the right hand ring 102 is in abutment on the hub90 through the teeth 104, 12, the torque is transmitted to the hub 10.

An increase in the torque in the same direction of rotation results incompression of the resilient members 112 of the predamper and rotationof the main damper until the right hand ring 88 is in abutment on thehub 10 through the teeth 92, 12.

Subsequently, when the transmitted torque increases even more in thesame direction, there is progressive compression of the resilientmembers 96 of the main damper, the left hand ring 88 turning withrespect to the right hand ring 88 which is in abutment on the hub 10.

Preferably, the rings 88 may be biased axially on the rings 102, whichmay themselves be biased axially on the median flange 90 of the hub, sothat vibrations and torque irregularities absorbed by the resilientmembers 112 of the predamper and 96 of the main damper are absorbed. Anyway known to the person in this technical field, comprising resilientrings, whether or not they are used in combination with friction rings,may be associated with the rings 88 and 102 and with the peripheralflange 90 in order to obtain the desired friction forces. Similarly, thesurfaces of the rings 88 and 102 and flange 90 in contact with eachother may be determined to that effect.

What is claimed is:
 1. A torsion damping device, mounted between twocoaxial rotating members for transmitting a rotary torque from onemember to the other with damping of vibrations and torque oscillations,comprising: two rings (16, 18, 46, 48) coaxial with the two rotatingmembers, rotational coupling means between the two rotating members andthe rings, and circumferentially acting resilient members (26) mountedbetween the rings in housings (24, 50) which are formed in the rings andwhich include means for abutment of the ends of the said resilientmembers, characterised in that the two rings (16, 18, 46, 48) arerotatable with respect to each other and with respect to the tworotating members (10, 68, 82) with a limited angular displacement, andare the rings urged in opposite directions of rotation by the resilientmembers (26) toward abutment on the means for coupling them to therespective ones of the rotating members.
 2. A device according to claim1, characterised in that the two rings (16, 18, 46, 48) are biasedaxially into abutment on the means (44, 140, 22, 12, 20) for couplingthem in rotation to the two rotating members.
 3. A device according toclaim 1, characterised in that each ring is biased into engagement onthe means for coupling it to one of the rotating members, and acircumferential clearance exists between the said ring and the means forcoupling it to the other rotating member.
 4. A device according to claim1, characterised in that each ring (16, 18, 48) includes a set of teeth(20) meshing, with a predetermined circumferential clearance, with a setof teeth (12) of one of the rotating members.
 5. A device according toclaim 4, characterised in that the set of teeth (20) of the rings areformed on their inner periphery, and the set of teeth (12) of therotating member (10) is formed on the outer periphery of a cylindricalsurface of the said member.
 6. A device according to claim 4,characterised in that the resilient members (26) bias the teeth (20) ofone ring into engagement on flanks (12 a) of the teeth (12) of therotating member and the teeth (20) of the other ring into engagement onthe opposed flanks (12 b) of the teeth (12) of the rotating member.
 7. Adevice according to claim 1, characterised in that the means forcoupling the said rings (16, 18, 46, 48) in rotation to one of therotating members comprise fingers or lugs (14, 140) fixed to the saidrotating member and engaged in circumferential slots (22, 54) of thesaid rings, the slots being of limited angular extent.
 8. A deviceaccording to claim 7, characterised in that the said fingers or lugs(14, 140) are substantially parallel to the axis of rotation.
 9. Adevice according to claim 5 characterised in that at least one said slot(22, 54) of one ring is positioned with respect to a slot (22, 54) ofthe other ring in such a way that the same finger or the same lug (14,140) fixed to the rotating member passes through the two said slots. 10.A device according to claim 1, characterised in that the meansconnecting the said rings (16, 18) to one of the rotating memberscomprise lugs (44) fixed to the rings and engaged between abutmentscarried by the rotating member.
 11. A device according to claim 10,characterised in that the said lugs (44) are substantially radial.
 12. Adevice according to claim 1, characterised in that the two rotatingmembers include sets of teeth meshing with each other with apredetermined circumferential clearance which is less than orsubstantially equal to the circumferential clearance of the rings (16,18) with respect to the two rotating members.
 13. A device according toclaim 1, characterised in that the two rings (16, 18) are identical. 14.A device according to claim 1, characterised in that the two rings (16,18) are formed by press-forming or stamping or by moulding with housings(24) for the said resilient members (26), each housing (24) including atone of its ends a face (30) for axial abutment of the resilient member(26) placed in the said housing.
 15. A device according to claim 13,characterised in that the other end (32) of the said housing is withoutany means for axial abutment of the said resilient member (26).
 16. Adevice according to claim 1, characterised in that the said housings(24) are defined in the said rings (16, 18) by recesses situated face toface as between one ring and the other, each recess being joined throughone end to a boss (28) projecting towards the other ring so as to definethe means (30) for axial abutment of a resilient member (26).
 17. Adevice according to claim 1, characterised in that the resilient membersare blocks of elastomer.
 18. A device according to claim 1,characterised in that the said rings (46, 48) are flat, and in that thehousings for the resilient members (26) are defined by recesses orwindows (50) in the rings, each recess or window having a radial sidewhich serves as an axial abutment for a resilient member (26) and whichincludes means (52) for centring and retaining the said member.
 19. Adevice according to claim 18, characterised in that the opposite radialside of the recess or window (50) is without any centring or retainingmeans for the resilient member (26).
 20. A device according to claim 18,characterised in that the two rings (46, 48) are in engagement on eachother.
 21. A device according to claim 1, characterised in that itconstitutes a unitary assembly, the two rings (16, 18) being in hookedengagement on each other by means of circumferential lugs (38) offsetaxially so as to engage within each other and to oppose axial separationof the rings.
 22. A device according to claim 1, characterised in thatit constitutes a predamper of a friction clutch for a motor vehicle. 23.A device according to one of claim 1, characterised in that it ispositioned axially on a cylindrical hub (10) by means of an open ring(40, 144) or a resilient ring (150) fitted in an annular groove in thehub (10).
 24. A device according to claim 22, characterised in that itis mounted inside a main damper between a guide ring (84) and an annulardamper plate (82) of the said main damper, or on the outside of the maindamper and substantially adjacent to a guide ring (68) of the said maindamper.
 25. A device according to claim 24, characterised in thatfriction means (146, 152) are gripped elastically between the predamperand the main damper.